In an optical communications network, an optical time domain reflectometer (OTDR) is an effective method for monitoring a fiber link. During optical pulse transmission, an optical fiber produces reflection and attenuation due to Rayleigh scattering, an optical fiber splice, a splice point, and other reasons.
Optical fiber performance (for example, a length of the optical fiber) that can be detected by the OTDR is affected by an attenuation coefficient of the optical fiber, and detection performance of the OTDR cannot be accurately reflected. Therefore, the detection performance of the OTDR is generally described by using a dynamic range.
The dynamic range of the OTDR represents a maximum optical loss that can be analyzed by the OTDR when a back-scatter level of an OTDR port drops to a specific noise level.
For example, the OTDR transmits optical pulses to a to-be-measured optical fiber, and detects reflected lights that are reflected back from the optical fiber and that have undergone reflection and attenuation. Information such as reflection and attenuation of the optical fiber, that is, an optical fiber attenuation curve, is obtained according to a relationship between intensity and time of reflected optical pulses. In this way, the optical fiber performance is detected, and the dynamic range of the OTDR is obtained.
Specifically, the optical pulses transmitted by the OTDR are classified into a single optical pulse and multiple optical pulses.
For a single optical pulse transmitted by the OTDR, the OTDR transmits a single optical pulse to the to-be-measured optical fiber to detect a reflected light from the optical pulse, so as to obtain an optical fiber attenuation curve of the detected reflected light.
However, when the optical fiber performance is being detected, there is a defect that an optical signal at the band needs to be turned off, that is, a data service is interrupted.
For multiple optical pulses transmitted by the OTDR, the OTDR transmits a pseudo-random (PN) optical pulse sequence (that is, a PN sequence) to the to-be-measured optical fiber to detect an optical signal reflected by the optical fiber, and perform correlation computation on the detected optical signal and the PN sequence, so as to obtain an optical fiber attenuation curve.
Although a data service does not need to be interrupted during optical fiber performance detection, and real-time detection of the optical fiber performance is implemented, the multiple optical pulses transmitted by the OTDR are distorted due to filtering of a transmitter, noise, and other reasons, causing that a weak reflected signal at a far end of the optical fiber is drown in noise. Consequently, the optical fiber performance that can be detected by the OTDR drops, that is, the dynamic range of the OTDR is reduced.